java是不可移植的。过滤和收集2。惰性过滤器？

Question

我尝试过滤AddReport类型的所有元素

但是当在谓词体中放置断点时，我看到那里的代码没有执行

它懒惰吗？我看到各种各样的子类

不仅仅是AddReport

    Iterable<BaseClass> filtered =
            Iterables.filter(myList,
                    new Predicate<BaseClass>() {
                        @Override
                        public boolean apply(@Nullable BaseClass input) {
                            AddReport addReport = (AddReport) input;
                            return ((addReport != null) && addReport.description.equals(messageBody));
                        }
                    });

    Collection<BaseClass> filtered2
            = Collections2.filter(myList,
            new Predicate<BaseClass>() {
                @Override
                public boolean apply(@Nullable BaseClass input) {
                    AddReport addReport = (AddReport) input;
                    return ((addReport != null) && addReport.description.equals(messageBody));
                }
            });

Answer 1

在我看来，您可能希望首先将iterable筛选为AddReport的实例，您可以这样做：

Iterable<AddReport> addReports = Iterables.filter(myList, AddReport.class);